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You don't have bad leaks and the therapy looks to be working at the beginning of the night.
I got a similar curve as you got (not as bad): at the beginning AHI is good at the end AHI is bad.
The solution is very simple: When we are in deep sleep phase and breathing nice with the CPAP, we feel so good that, we lay in our backs and begin the problems.
Of curse I am guessing in your case. There are different methods to avoid sleeping in your back described in the forum, I haven't test them because I got another problems.
Pay attention to this and let me know what you do, because it will be a time that I will beginning to cope with this problem.
That doesn't mean that later you can fine tuning your therapy.
Ralph.

Hi, toinewi. I am not a BiPap user, but I have the same OA clusters late in my sleep, resulting in the "camel humps" in the hourly AHI graph. If you had an in-lab diagnostic sleep study, you might check it to see if your AHI values were calculated for various sleep positions and sleep stages. I'll bet you'll find that your obstructive apnea is much worse during REM sleep.

I think you could improve your overall AHI score by increasing your EPAPmin value to something more like 14. Even if you don't need that much pressure for your events in the first half of the night, a higher EPAPmin value would mean that the algorithm doesn't have as far to go when it suddenly needs to increase your pressure to 25.

Your actual IPAP pressure needs during the night may be 14-25, but my conclusion from watching the behavior of the PR algorithm has been that it cannot handle that large a range and give good results.

If you discover that 25 cm isn't enough pressure to control your OAs, then I'm not sure what you do. Probably avoid sleeping on your back.

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